IMGAPI-451: increase description and tags MAX_*_LENGTHs for image manifest
IMGAPI-451: increase description and tags MAX_*_LENGTHs for image manifest

numericillustration/sdc-imgapi,numericillustration/sdc-imgapi,joyent/sdc-imgapi,joyent/sdc-imgapi,joyent/sdc-imgapi,numericillustration/sdc-imgapi